It is often necessary to change the position of a payload carried aboard a spacecraft, for example to alter the pointing direction of a telescope. To do so, torque is applied to the payload and a corresponding reaction torque is thereby applied to the vehicle. The result is the desired motion of the payload accompanied by undesired motion of the vehicle. If vehicle motion is unacceptable, an attitude control system (ACS) on the vehicle must act to control it, generally requiring use of electrical power and/or propellant. If the ACS cannot accept the burden, then the payload must be designed to be reactionless. This usually is accomplished with a countermoving mass to absorb the reaction torque so that the net torque on the vehicle is essentially zero. This method, however, significantly increases the weight of the system.